javascript - 如何使用jquery在大dom中获得良好的性能？

Question

我用 Javascript 和 jquery 编写了一个小程序。

   var mlife = function (i, j, alive) {
    var face = '<div class="life" id="l_' + i + '_' + j + '"/>';
    var f = $(face);
    var ps = new Array();
    //var interval;
    this.draw=function() {
        if (alive) {
            f.addClass('l');
        } else {
            f.removeClass('l');
        }
    };
    this.aliveCheck=function() {
        var alivecount = 0;
        for (var i = 0; i < ps.length; i++) {
            var el = $('#l_' + ps[i]);
            if (el.length > 0) {
                if (el.hasClass('l')) {
                    alivecount++;
                }
            }
        }
        if (alive) {
            if (alivecount < 2) {
                alive = false;
            } else if (alivecount == 2 || alivecount == 3) {
                alive = alive;
            } else if (alivecount > 3) {
                alive = false;
            }
        } else {
            if (alivecount == 3) {
                alive = true;
            }
        }
        //_draw();
    };
    this.getface = function () {
        return f;
    };
    function _init() {
        ps.push((i - 1) + '_' + (j - 1));
        ps.push((i - 1) + '_' + (j + 1));
        ps.push((i + 1) + '_' + (j - 1));
        ps.push((i + 1) + '_' + (j + 1));
        ps.push(i + '_' + (j - 1));
        ps.push(i + '_' + (j + 1));
        ps.push((i + 1) + '_' + j);
        ps.push((i - 1) + '_' + j);
        if (alive) {
            f.addClass('l'); 
        }

    };
    _init();
}
$(function () { 
    var html = "";
    var alive = false;
    var cells = new Array();

    for (var i = 0; i < 100; i++) {
        for (var j = 0; j < 100; j++) {
            if (Math.random() > 0.90) {
                alive = true;
            } else {
                alive = false;
            }
            var l = new mlife(i, j, alive);

            cells.push(l);
            $('#show').append(l.getface()); 
        }
    }

    setInterval(allAliveCheck,1000);


    function allAliveCheck(){

        for(var i=0;i<cells.length;i++){
            cells[i].aliveCheck();
        }
        for(var i=0;i<cells.length;i++){
            cells[i].draw();
        }

    }







});

http://jsfiddle.net/chanjianyi/upgvzm78/1/

这是关于“生命的游戏”:http://en.wikipedia.org/wiki/Conway%27s_Game_of_Life

但我发现控制大量div的性能非常糟糕。

有人有优化我的程序的想法吗？

Answer 1

jQuery 很慢。抛弃 jQuery，它运行得更快。这是一个例子。

var mlife = function(i, j, alive) {
  // var face = '<div class="life" id="l_' + i + '_' + j + '"/>';
  var f = document.createElement('div');
  f.className = 'life';
  f.id = 'l_' + i + '_' + j;
  var ps = [];
  //var interval;
  this.draw = function() {
    if (alive) {
      f.classList.add('l');
    } else {
      f.classList.remove('l');
    }
  };
  this.aliveCheck = function() {
    var alivecount = 0;
    for (var i = 0; i < ps.length; i++) {
      var el = document.getElementById('l_' + ps[i]);
      if (el) {
        if (el.classList.contains('l')) {
          alivecount++;
        }
      }
    }
    if (alive) {
      if (alivecount < 2) {
        alive = false;
      } else if (alivecount == 2 || alivecount == 3) {
        alive = alive;
      } else if (alivecount > 3) {
        alive = false;
      }
    } else {
      if (alivecount == 3) {
        alive = true;
      }
    }
    //_draw();
  };
  this.getface = function() {
    return f;
  };

  function _init() {
    ps.push((i - 1) + '_' + (j - 1));
    ps.push((i - 1) + '_' + (j + 1));
    ps.push((i + 1) + '_' + (j - 1));
    ps.push((i + 1) + '_' + (j + 1));
    ps.push(i + '_' + (j - 1));
    ps.push(i + '_' + (j + 1));
    ps.push((i + 1) + '_' + j);
    ps.push((i - 1) + '_' + j);
    if (alive) {
      f.classList.add('l');
    }

  };
  _init();
}


var html = "";
var alive = false;
var cells = [];

for (var i = 0; i < 100; i++) {
  for (var j = 0; j < 100; j++) {
    if (Math.random() > 0.90) {
      alive = true;
    } else {
      alive = false;
    }
    var l = new mlife(i, j, alive);

    cells.push(l);
    document.getElementById('show').appendChild(l.getface());
  }
}

setInterval(allAliveCheck, 1000);


function allAliveCheck() {

  for (var i = 0; i < cells.length; i++) {
    cells[i].aliveCheck();
  }
  for (var i = 0; i < cells.length; i++) {
    cells[i].draw();
  }

}

#show {
  width: 500px;
  height: 500px;
  border: 0px solid red;
}
.life {
  width: 5px;
  height: 5px;
  background: black;
  float: left;
}
.l {
  background: blue;
}

<body>
  <div id="show"></div>
</body>

考虑将比赛 field 数据存储为简单数组，而不是将其存储在 HTML 元素中。这样您就可以使任意前端显示相同的数据。 Canvas 或简单的预格式化文本 block 可以在视觉上给出相同的结果；任何一个都可能比一堆 div 表现得更好。

我建议将您的代码发布到 codereview.stackexchange.com 上。这段代码还有很大的改进空间； CR 是学习如何改进它的好地方。

这是一个简单 CA 的示例(这是我几周前为了好玩而做的事情)。它使用一堆 button 元素来显示网格，但请注意如何使用 Canvas 或其他机制轻松交换显示例程。

//
// Cell
//

function Cell(grid, x, y) {
    /** @type Grid */
    this.grid = grid;
    /** @type number */
    this.x = x;
    /** @type number */
    this.y = y;
}

Cell.prototype.getAdjacent = function() {
    var cellX = this.x,
        cellY = this.y,
        grid = this.grid,
        result = [],
        cell;
    
    for (var y = cellY - 1; y <= cellY + 1; y++) {
        for (var x = cellX - 1; x <= cellX + 1; x++) {
            if (x == cellX && y == cellY) {
                continue;
            }
            cell = grid.getCell(x, y);
            cell && result.push(cell);
        }
    }
    return result;
};

//
// Grid
//

function Grid(width, height) {
    /** @type number */
    this.width = width;
    /** @type number */
    this.height = height;
    /** @type Array.<Cell> */
    this.cells = [];
    
    this.initCells();
}

Grid.prototype.initCells = function() {
    var width = this.width,
        height = this.height,
        cells = this.cells;
        
    for (var y = height; y--;) {
        for (var x = width; x--;) {
            cells.unshift(new Cell(this, x, y));
        }
    }
};

Grid.prototype.getCell = function(x, y) {
    var width = this.width,
        height = this.height,
        cells = this.cells;
        
    if (x >= 0 && y >= 0 && x < width && y < height) {
        return cells[x + y * width];
    }
};

Grid.prototype.each = function(callback) {
    var cells = this.cells,
        cellCount = cells.length;
        
    for (var i = 0; i < cellCount; i++) {
        callback(cells[i], i);
    }
};


//
// GridDisplay
//

function GridDisplay(grid, element) {
    /** @type Grid */
    this.grid = grid;
    /** @type Element */
    this.element = element;
}

GridDisplay.prototype.drawCell = function(cell) {
    var display = this,
        button = document.createElement('button');
        
    button.style.border = '1px outset white';
    if (cell.value) {
        button.style.backgroundColor = 'black';
    }
    button.onclick = function(event) {
        if (cell.value) {
            cell.value = false;
        } else {
            cell.value = true;
        }
        display.draw();
    };
    
    return button;
};

GridDisplay.prototype.draw = function() {
    var display = this,
        grid = this.grid,
        buttons = this.element.getElementsByTagName('button'),
        container;
        
    if (buttons.length) {
        grid.each(function(cell, i) {
            if (cell.value) {
                buttons[i].style.backgroundColor = 'black';
            } else {
                buttons[i].style.backgroundColor = null;
            }
        });
        return;
    }
    
    this.element.innerHTML = '';
    container = document.createElement('div');
    
    grid.each(function(cell, i) {
        if (!cell.x) {
            container.appendChild(document.createElement('br'));
        }
        container.appendChild(display.drawCell(cell));
    });
    
    this.element.appendChild(container);
};


//
// Game
//

function Game(width, height, rule) {
    // The standard Game of Life is symbolised as "B3/S23": 
    // A cell is "Born" if it has exactly 3 neighbours, 
    // "Stays alive" if it has 2 or 3 living neighbours.
    var bornSurvive = rule.match(/\d+/g);
    
    this.birthRule = bornSurvive[0];
    this.survivalRule = bornSurvive[1];
    this.grid = new Grid(width, height);
    this.gridDisplay = new GridDisplay(this.grid, board);
    this.gridDisplay.draw();
}

Game.prototype.tick = function() {
    var grid = this.grid,
        survivalRule = this.survivalRule,
        birthRule = this.birthRule;
    
    grid.each(function(cell, i) {
        var neighbors = cell.getAdjacent();
        var liveNeighborCount = 0;
        
        for (var j = 0; j < neighbors.length; j++) {
            if (neighbors[j].value) {
                ++liveNeighborCount;
            }
        }
        if (cell.value) {
            cell.nextValue = ~survivalRule.indexOf(liveNeighborCount);
        } else {
            cell.nextValue = ~birthRule.indexOf(liveNeighborCount);
        }
    });
    grid.each(function(cell) {
        cell.value = cell.nextValue;
    });
    this.gridDisplay.draw();
};


function createButton(label, callback) {
    var button = document.createElement('input');
    button.type = 'button';
    button.value = label;
    button.onclick = callback;
    document.body.appendChild(button);
}

var board = document.getElementById('board');
var game;
var interval;

createButton('new game', function() {
    clearInterval(interval);
    board.innerHTML = '';
    game = new Game(50, 50, prompt('Enter a rule', 'B3/S23'));
});

createButton('randomize', function() {
    var cells = game.grid.cells;
    clearInterval(interval);
    for (var i = 0; i < cells.length; i++) {
        cells[i].value = Math.random() * 2 | 0;
    }
    game.gridDisplay.draw();
});

createButton('step', function() {
    clearInterval(interval);
    game.tick();
});

createButton('go', function() {
    clearInterval(interval);
    interval = setInterval(function () {
        game.tick()
    }, 100);
});

createButton('stop', function() {
    clearInterval(interval);
});

body { font: 10pt sans-serif; }
div { font-size: 1px; }
button { width: 8px; height: 8px; margin:0; padding: 0; vertical-align: middle; }

<div id="board"></div>